…new research shows that many ants in a colony seem to specialize in doing nothing at all. To get a closer look at how these ants filled their time, researchers marked every member of five lab-based colonies with dots of colored paint. Over the course of 2 weeks, a high-definition camera recorded 5-minute segments of the ants in action six times a day, capturing their behavior (or lack thereof). Out of the “workers,” 71.9% were inactive at least half the time, and 25.1% were never seen working. A small fraction of the ants, just 2.6%, were always active during observation…

…

. According to the team, this suggests that inactivity isn’t merely a break between tasks, but might be an important part of the ants’ division of labor. Just what part remains unclear, but one theory is that the inactive ants are either too young or too old to work. Future studies over longer periods of time could capture the ants switching between busy and lazy modes.

Perhaps the quarter of the ants that are generally idle are basically reservists to be used in the event of a threat to the colony that requires either defense or moving or both?

This seemed the most plausible theory to me. That there’d be some sort of reserve of ants who’d need to defend the colony if something happens. And what does that mean, exactly? Well, it apparently doesn’t mean that the worker ants need to be training all of the time or on the move. Instead, apparently slacking gets a lot of things done for ants!

Here was a response to that comment:

I suspect it is something along those lines. Part of being efficient (something ant colonies are very good at) is not using energy when it’s unnecessary. If having 25% of the colony active is enough to keep the colony running in peacetime, then it doesn’t make sense to have more than that active.

Also, the ants that are regularly inactive could just be a consequence of how ants communicate. If a task needs to be done and a certain number of ants need to do it, that message waves through the colony until the number of ants required are on the job. It’s all location-based, and there’s no discriminating there between ants who have or have not worked a lot. There may be large hotspots in ant colonies where ants are sent to work when only the heaviest of workloads appears. The ants are all coded the same way, so the lazy ants aren’t lazy, they just haven’t been assigned anything.

That said, I’m not purchasing the study either, so I don’t know if there’s anything in there that can dispute that.

Edit: Here’s an interesting study into the metabolic rate of Harvester ant colonies.

TL;DR: The total metabolic rate of ant colonies doesn’t scale up with the metabolic rates of an individual ant living on its own. As colonies get bigger, the energy spent per ant goes down by a large amount. That rate is proportional to total mass with an exponent of 0.75, about the same rate we see in larger individual organisms. (For a typical Harvester ant colony of 4000 ants, this works out to an energy throughput of about 500 individual ants.) The study also notes that larger colonies have more disparity in ant activity levels.

In the end, I don’t have a lot to say about this as ants aren’t my specialty and I am too much of a cheapskate to buy the publication the research was published in.

But at least it seems to be the case that the workplace isn’t the only place that involves a substantial part of their work depending on a small minority, while the rest of us just try to relax as much as possible.